During the past two decades， research has greatly expanded our knowledge about sleep and dreams. Scientists have identified various stages of sleep， and they have found that humans can function well on very little sleep， but only if they dream. ⑸Yet the true function of sleep and dreaming continues to elude precise explanation.

Function v. 运转

only if ：只有

if only ：引导虚拟条件句，要是…就好了。

译文：科学家已经确认了各种不同的睡眠阶段，并且已经发现人类肌体可以运行的很好，但是只是在做梦的情况下。

In 1970 Milton Kramer and Thomas Roth， researchers at the VA Hospital and the University of Cincinnati College of Medicine， respectively， raised this question： Do our moods in the morning relate in any way to our sleep and dreams the previous night？

Human experience suggests that they do. Certainly we generally feel better after a good night‘s sleep. But Drs. Kramer and Roth sought a much more definitive answer. And that answer， though sill evolving is a positive yes.

Kramer and Roth began by seeking to determine whether one‘s mood differs between night and morning， and whether this is related directly to sleep.⑹ They found that there is a difference， and it is definitely related to sleep. Then they explored the various aspects of mood and their relationship to the various stages of sleep and dreaming.

be related to 与…有关系

译文：Kramer和Roth企图确定人们的情绪早晚是否不同，并且这是否直接与人们的睡眠有关。

What does a good night‘s sleep mean to our mood？ Generally we are happier， less aggressive， sleepier， and， a bit surprisingly， less friendly. Being sleepier is easily explained. It simply takes a little time to become fully alert after awakening.

But why should we feel less friendly？ here the researchers must speculate a little. They suggest the answer may be the lack of association with

other humans during the period of sleep.

Once the two doctors established scientifically what common sense and folk wisdom had long taught - namely， that there is link between sleep and how we feel -they set out to learn what parts of our mood are related to which specific parts of the sleep cycle. ⑺

Normal sleep is broken into five distinct parts - Stages I through 4， plus REM， an acronym for rapid eye movement. Much remains unknown about each of the five sleep stages. Most dreaming occurs during REM sleep， a period when the eyeballs move rapidly beneath the closed lids. And whether they remember or not， all adults dream， usually four to six times a night.

Three types of mood are strongly related to some specific stage of sleep. Our friendly， aggressive， and sleepy feelings all relate to Stage 2 sleep， which accounts for most of our total sleep hours. ⑻Our friendly and sleepy feelings， but not our aggressive feelings， are affected as well by Stages 3 and 4， and by how long it takes us to fall asleep.

account for 占…比例

译文：我们的友善、好斗、倦意都与占我们绝大部分睡眠时间的睡眠的第二阶段有关。

This means that if you get less sleep than normal -and people vary a great deal in how much sleep they normally require -you awake more friendly， more aggressive， and less sleepy.

At this point， the doctors found themselves puzzled. They knew from their earlier work that sleep determines if people feel happier. Yet when they studied the various sleep stages， they found no correlation between sleep physiology and the unhappy mood. Clearly sleep made a difference， but that difference didn‘t relate to how much time one spent in each of the various sleep stages.

The two researchers decided the key to whether we feel happy or unhappy after sleep must lie in sleep‘s psychological component -our dreams.⑼ So they began studying dream content -what dreamers dreamed and who appeared in their dreams -to see how this affected mood.

“We feel happy or unhappy after sleep”这个句子是介词宾语从句的主语，是一个主语从句。

译文：两个研究人员决定我们睡醒后是否高兴的关键在于我们睡觉时的心理组成成份——我们的梦。

Instead of sleeping through the night， volunteers now were awakened four times while in REM sleep. They were asked about such things as what their dreams were about； the sex， age， identity， and number of the people in their dreams； and what each person in a dream was doing.

Interestingly， Kramer and Roth found that being awakened four times a night didn‘t make a difference in the volunteers’ morning mood patterns. But they did find that who appears in a dream has a far greater influence on mood than what occurs in the dream. “Who affects all the moods.” Kramer says， “but primarily the unhappy mood.”

Each of us， it turns out， has a special dream character，⑽ and if this type of character appears in our dreams， we are happier when we awake. “For people in general， how unhappy you feel after sleep depends on who is in the dream.” Kramer says. “Who it is that makes you happier is different for you than for me.”⑾ For some it may be an older woman， for example； for others， a young man.